I need some mythbusting help

[Extremeweatherguy]

the 1938 hurricane was a 5 east of hat. It weakened to a 105KT 3 in the 7 hours it took to reach Long Island

a 3 hitting NYC will devastate NJ, ALL of Long Island and Conn as well. Be prepared for dramatic changes of the American way of life after that as damage may reach into the trillions, and the deaths will likely be in the hundreds of thousands

Trillions of dollars in damage? Hundereds of thousands dead? What study is that from, because that seems to be a GROSS exaggeration to me.

I agree. Official damages from Katrina are 75 billion...so for the number to exceed a trillion dollars..we would need to see most of the metro area of the NE destroyed (completely). The only way I could see a trillion dollars being reached would be a Cat. 5 grazing by DC with 110mph gusts at the capitol building (to the left of the eye), and then it would need to move right along the coast of New Jersey and Rhode Island before making landfall in New York City as a Strong Cat. 3, but with a Cat. 5 surge. The surge would flood much of the city and the winds would blow out many windows, as well as damage homes, businesses and other items. Wind gusts would top 150mph at the NYC airports. Finally, the storm would move into Conneticut and Massachusatts and reach Boston as a weakening Cat. 1, enough to knock down some trees, take off some shingles, down signs and blow out a few windows. After moving back out to sea it would maintain 80-90mph as it became extratropical. It would then skirt up along Maine leading to beach erosion and wind damage to all coastal cities. All and all, I do not even think that scenario would reach a trillion...may be 500 billion..but for a trillion we would need to see a Cat. 5 in NYC (after hitting another major city) which has about a 1 in 1,000,000,000,000,000 chance of happening.

[mike815]

well maybe not quiet that bad but it still would be staggering.

[wxmann_91]

the 1938 hurricane was a 5 east of hat. It weakened to a 105KT 3 in the 7 hours it took to reach Long Island

a 3 hitting NYC will devastate NJ, ALL of Long Island and Conn as well. Be prepared for dramatic changes of the American way of life after that as damage may reach into the trillions, and the deaths will likely be in the hundreds of thousands

Trillions of dollars in damage? Hundereds of thousands dead? What study is that from, because that seems to be a GROSS exaggeration to me.

Not an exaggeration. NYC hurricane will affect the economy around the world. Trillions easy. Just look at how much the Great Depression did. Now times that by 100 and you get the effect of a Cat 3 NYC hurricane.

Look how many people live in NYC. If 95% evacuated, there would still be hundreds of thousands that are in NYC. And if NYC is wiped out like Holly Beach was wiped out in Rita, probably there 25-50% of the people there would perish. (100,000-250,000 people)

[StormSkeptic]

Highly unlikely and grossly exagerated.

- Cat 5 into NY virtually impossible. As we have seen, even a CAT 5 into the northern gulf where water temps are very warm and the air more humid is difficult to impossible
- Something on the order of a fast moving cat 3, similar to the 1938 storm, is something that is the max possible, and even that is a rare event requiring a very unique set of circumstances - i.e, the storm merging with a trough and maintaing intensity during extra-tropical transition
- The angle needs to be just right in order to get SE and east winds funnelling into the NY Harbor area. THis would require a storm to be traveling due north or even NNW and hit just to the left of the city. Very difficult to do, don't think it has happened in the last 150 years. Most storms travel NNE or NE by the time the get to the lattitude of NY, due to interaction with the westerlies. To go N or NNW, would require interaction with a trough which would most likley weaken the storm due to dry air and shear. Remeber the 1938 storm hit well east of the city, so while it did get strong wind gusts, nothing catastrohic and no real surge since the winds were blowing offshore. Even if there was the rare event where the trough interaction helped to maintain the storm it would need to be moving fast, and that would not allow much time for a surge to build up.
- Thus, the only way to be a cat 3 would be interaction with a trough, which usually moves the storm east of North and moves fast. Hard to have that and a path that takes it west of NY and slow enough to build up a surge
- While this worst case scenario, being a very rare event, might flood parts of the city, this is not NO. The city is not below sea level and most of manhattan consists of high rises. They would flood, but even if people did not get out, they could move higher up and be safe. Areas by JFK, which is a swamp, would flood and this would be very bad, but a very high death toll, I can't see. Subways may flood and that would be bad, but this happens all the time, everytime an old watermain breaks. Widespread flooding would be bad, but not devastating.
- Buildings would not topple. The skyscrapers are designed for very high winds. MAybe not CAT 5, but they would not see that. Also, Manhattan is built on solild bedrock. Flooding itself would not undermine them

In short, your scenario is way over the top. Yes, NY may be vulnerable to a very very rare but devasting event, but even at the worst not nearly the picture you paint.

[milankovitch]

Not an exaggeration. NYC hurricane will affect the economy around the world. Trillions easy. Just look at how much the Great Depression did. Now times that by 100 and you get the effect of a Cat 3 NYC hurricane.

Look how many people live in NYC. If 95% evacuated, there would still be hundreds of thousands that are in NYC. And if NYC is wiped out like Holly Beach was wiped out in Rita, probably there 25-50% of the people there would perish. (100,000-250,000 people)

http://www.aoml.noaa.gov/hrd/tcfaq/costliesttable3.html

Using 2004 Inflation, Population, and Wealth Normalization

New England 1938 23.451 billion

I also remember studies that said 45 and 100 billion for a cat 4 into New York City, but I can't find it now. I think 100 billion (cat 3 into New York) in damage seems more reasonable in light of Katrina. I could see 200-300 billion at the absolute maximum. I know of only one scenario that has damage estimates in the trillion range (I have seen as high as 3 trillion, most around 1 trillion), a repeat of the Kanto 7.9-8.4 magnitute quake in the heart of Tokyo. Maybe that should give you an idea of the amount of damage your talking about when you throw trillions around.

Now if you can find a study by a respectable organization that predicts trillions of damage for a category 3 into New York City I'd like to see it but I'm not interested in wild guesses. As for 100,000s of deaths what was the death toll from the 1938 storm 600? That certainly isn't the worst case storm (strength or location) but it gives you somewhere to start, how can you go up by a factor of several hundered? The population hasn't increase that much, I couldn't find the population of the New England area in 1938. But the population of New York City proper was 7,454,995 then and is 8,104,079 now so populations in New England probably haven't increased by factors of 100 since then. Factor in modern warnings and forecasting and I'm thinking probably several hundred and several thousand at the absolute most. Now this is a disaster of epic proportions and it has the potential to rival Katrina but some of you are getting carried away.

[WxGuy1]

the 1938 hurricane was a 5 east of hat. It weakened to a 105KT 3 in the 7 hours it took to reach Long Island

a 3 hitting NYC will devastate NJ, ALL of Long Island and Conn as well. Be prepared for dramatic changes of the American way of life after that as damage may reach into the trillions, and the deaths will likely be in the hundreds of thousands

How was it able to maintain Cat 5 intensity all the way up to Hat? Was it because its forward motion contributed to that windspeed?

Actually, for an East Coast storm, land will most often be on the left side of the storm. Assuming the storm is moving northward by the time it gets to the New England coast, a fast forward motion will likely result in WEAKER ground-relative winds than would otherwise result. For example, if the storm is 155mph axisymmetric and is moving northward at 45mph, then the left side of the storm will see winds of 110mph (155-45). Of course, if the storm is moving NW, a fast forward motion may yield increase winds for those locations in the right part of the storm, but the majority of east-coast storms tend to move Nward or NEward (after clipping land). That said, fast forward motion may mean that the storm was less time to weaken over the cooler SSTs, in which case fast motion may indeed contribute to an abnormally strong storm that far north (but the motion itself wouldn't enhance the winds in most cases).

In addition, I'm not sure I'd say that fast forward motion usually causes an extratropical transition. Usually, fast forward motion indicates an environment that favors an extratropical transition due to the thermal wind relationship -- thermal gradients / baroclinity in the low-levels yields stronger winds aloft. So the stronger flow aloft often indicates low-level baroclinicity, which can lead to an extratropical transition. In this case, fast forward motion likely wouldn't be a CAUSE for the extratropical transition, but an EFFECT of low-level thermal gradients that can drive an extratropical transition.

[wxmann_91]

Highly unlikely and grossly exagerated.

- Cat 5 into NY virtually impossible. As we have seen, even a CAT 5 into the northern gulf where water temps are very warm and the air more humid is difficult to impossible
- Something on the order of a fast moving cat 3, similar to the 1938 storm, is something that is the max possible, and even that is a rare event requiring a very unique set of circumstances - i.e, the storm merging with a trough and maintaing intensity during extra-tropical transition
- The angle needs to be just right in order to get SE and east winds funnelling into the NY Harbor area. THis would require a storm to be traveling due north or even NNW and hit just to the left of the city. Very difficult to do, don't think it has happened in the last 150 years. Most storms travel NNE or NE by the time the get to the lattitude of NY, due to interaction with the westerlies. To go N or NNW, would require interaction with a trough which would most likley weaken the storm due to dry air and shear. Remeber the 1938 storm hit well east of the city, so while it did get strong wind gusts, nothing catastrohic and no real surge since the winds were blowing offshore. Even if there was the rare event where the trough interaction helped to maintain the storm it would need to be moving fast, and that would not allow much time for a surge to build up.
- Thus, the only way to be a cat 3 would be interaction with a trough, which usually moves the storm east of North and moves fast. Hard to have that and a path that takes it west of NY and slow enough to build up a surge
- While this worst case scenario, being a very rare event, might flood parts of the city, this is not NO. The city is not below sea level and most of manhattan consists of high rises. They would flood, but even if people did not get out, they could move higher up and be safe. Areas by JFK, which is a swamp, would flood and this would be very bad, but a very high death toll, I can't see. Subways may flood and that would be bad, but this happens all the time, everytime an old watermain breaks. Widespread flooding would be bad, but not devastating.
- Buildings would not topple. The skyscrapers are designed for very high winds. MAybe not CAT 5, but they would not see that. Also, Manhattan is built on solild bedrock. Flooding itself would not undermine them

In short, your scenario is way over the top. Yes, NY may be vulnerable to a very very rare but devasting event, but even at the worst not nearly the picture you paint.

I'd suggest you look at data from the 1890's. You'd be surprised. Another thing - no Cat 5 is necessary to level NYC. A Cat 1 at the right angle can be as costly and deadly as Katrina.

[ericinmia]

People don't make blind posts...

You would be very surprised to find out that most of the buildings in the NE USA can only handle 100+ or so mph gusts... if this wind comes across at a a diagonal to the structure, and impacts a corner... i saw a study that the empire state building or some other equivalent couldn't withstand more than 70mph. sustained...

Like Dereck said, were not talking a cat5... were talking a VERY RARE, almost never strike of a cat 3 or stronger. Which would cause close to immeasurable damage.
-Eric

[Derek Ortt]

to say flooding is not a problem for NYC shows how little one understands about NYC

In 1821, from a mere cat 2, the Hudson and East Rivers merged over the center of Manhattan. From a Borderline 1/2 in 1893, the same thing nearly happened

Look at some photos of cat 2 surge simulations into NYC... the Brooklyn Battery tunnel is under water... the entire structure

the surge is much worse for NYC than New Orleans

and vertical evacuation... thats advice I'd expect Dr Kevorkian to give. Cat 3 winds will destroy the high rises. They will remain standing, but nearly all windows will be blown out and interior contents will be blown out. Winds will be even hgiher aloft than usual, since at those latitudes, the highest winds are higher in the atmosphere

1938 didn't hit the city; thus, it is not a valid example of what a cat 3 will do to NYC

[Extremeweatherguy]

the 1938 hurricane was a 5 east of hat. It weakened to a 105KT 3 in the 7 hours it took to reach Long Island

a 3 hitting NYC will devastate NJ, ALL of Long Island and Conn as well. Be prepared for dramatic changes of the American way of life after that as damage may reach into the trillions, and the deaths will likely be in the hundreds of thousands

Trillions of dollars in damage? Hundereds of thousands dead? What study is that from, because that seems to be a GROSS exaggeration to me.

Not an exaggeration. NYC hurricane will affect the economy around the world. Trillions easy. Just look at how much the Great Depression did. Now times that by 100 and you get the effect of a Cat 3 NYC hurricane.

Look how many people live in NYC. If 95% evacuated, there would still be hundreds of thousands that are in NYC. And if NYC is wiped out like Holly Beach was wiped out in Rita, probably there 25-50% of the people there would perish. (100,000-250,000 people)

We are not talking about the economy around the world. We are talking about the total insured losses. When they say the damage cost of a hurricane...that is what they are talking about. IF we calculated the economic losses around the world too, then every hurricane would be a billion or more dollar storm, and most would top 50 billion.

[Extremeweatherguy]

to say flooding is not a problem for NYC shows how little one understands about NYC

In 1821, from a mere cat 2, the Hudson and East Rivers merged over the center of Manhattan. From a Borderline 1/2 in 1893, the same thing nearly happened

Look at some photos of cat 2 surge simulations into NYC... the Brooklyn Battery tunnel is under water... the entire structure

the surge is much worse for NYC than New Orleans

and vertical evacuation... thats advice I'd expect Dr Kevorkian to give. Cat 3 winds will destroy the high rises. They will remain standing, but nearly all windows will be blown out and interior contents will be blown out. Winds will be even hgiher aloft than usual, since at those latitudes, the highest winds are higher in the atmosphere

1938 didn't hit the city; thus, it is not a valid example of what a cat 3 will do to NYC

New Orleans however is like a bowl and much harder to pump the water out of. In New York, the water would receed after the hurricane passed.

[Derek Ortt]

the surge also receded in Mississippi... not that it made any difference

the surge for NYC would be AT LEAST as high as a MS surge, likely higher since it sits right on the corner of he coast

[terstorm1012]

to say flooding is not a problem for NYC shows how little one understands about NYC

In 1821, from a mere cat 2, the Hudson and East Rivers merged over the center of Manhattan. From a Borderline 1/2 in 1893, the same thing nearly happened

Look at some photos of cat 2 surge simulations into NYC... the Brooklyn Battery tunnel is under water... the entire structure

the surge is much worse for NYC than New Orleans

and vertical evacuation... thats advice I'd expect Dr Kevorkian to give. Cat 3 winds will destroy the high rises. They will remain standing, but nearly all windows will be blown out and interior contents will be blown out. Winds will be even hgiher aloft than usual, since at those latitudes, the highest winds are higher in the atmosphere

1938 didn't hit the city; thus, it is not a valid example of what a cat 3 will do to NYC

Derek, the 1821 storm did not flood where the highrises are today (Times Square, Midtown). In 1821, that area wasn't even inhabited. Times Square and Midtown were developed during and after the Civil War.

The Hudson and East met around Wall St.

Midtown Manhattan is at least 50 feet above sea level and probably higher.

Subways, highways would flood yes, they flooded during Floyd and the 1992 Nor'Easter, undermining foundations not likely...you can tell where the bedrock is close to the surface by looking at the profile of Manhattan.

I also don't think buildings would topple unless they got several tens of hours of wind---a 'cane at this latitude would be in and out in 6-12 hours, the worst winds lasting no more than 3.

[Derek Ortt]

the buildings will not topple. However, as was experienced in New Orleans and Mismi/Lauderdale, cat 1 or 2 winds will destroy the high rises without any problem. Wind, not water is the concern for the high rises. They wont collapse, but there will be nothing left.

The price tag will be so high as those high rises are very expensive. Thats the main reason why Wilma caused so much damage, took out some high rises and we have 15-20 billion. High rises in NYC are more common, and much higher

The death toll will come from the surge and the inability to evacuate, plus those who use vertical evacuation are going to be in big trouble. No way can NYC be evacuated, and officials there know it

[terstorm1012]

Uh NYC has one of the nations better disaster mitigation plans and research centers--for anything imaginable. Read a paper once on a middle magnitude 5 quake hitting the city, which would be pretty damaging for this part of the country. (Skyscrapers and highrises would hold though, its masonry that the study was worried about).

At present they're updating it. It isn't the officials fault on this one but the general population not taking threats seriously.

There is a number you can call to get evac maps from the city. So it's not like the city is sitting on its hands. They even have places designated as shelters, given most of the city is pretty far above sea level and surge level. So if the city can't empty, which it can't, there are plenty of safe places that people could get to that are safe.

Unfortunately, NYC is not a lower latitude city where you can see it coming days away. At our latitude storms are rocketing poleward---you'd have only hours.

I also don't see where hundreds of thousands could die, thousands perhaps if even...NYC is not flat, most of it is far enough above sea level that it would not flood.

Of course we'll have to wait for this unlikely scenario to happen to see if we're right or wrong or not.

[Derek Ortt]

a magnitude 5 quake as a way of planning for a disaster? That, to be honest, is a total jokeThere differences between a 5 and a 6 are exponential (had a 5 in Ohio the same day Georges hit the Keys... little damage)

yes, the sky scrapers will hold in a mag 5 quake, likely in a 6 as well

I NEVER mentioned them collapsing as the winds wont be strong enough (even the surge for the ones on the coast wont collapse)

also, NYC is not just Manhattan. A cat 3 will likely put JFK airport under 20-30 feet of water based upon model simulations. West LI on the coats would be leveled, except for the sky scrapers, which would be gutted

[vbhoutex]

Ok, HF is writng a horror story, not a reality story. Over the top? Yes!!! That is what many horror stories are. If this is supposed to have a really good dose of reality with it, then go with the CAT3 scenarios. Still would be a HORRENDOUS CALAMITY if a true CAT3 hit NYC at the N to NNW angle and the city was in the NE quad.

[terstorm1012]

I wasn't really arguing with ya Derek, btw, just putting up a devil's advocate

HurFloyd, a suggestion for your horror/sci fi story is the book Mother of Storms by John Barnes, where NYC gets wiped out by a storm that erases Florida and sends a wall of water a mile high over Ireland, UK and inland past St. Petersburg Russia. Tho it's a book I'd give a NC-17 rating to if it were a movie, and I don't know your age...so you may or may not want to avoid it.

[Derek Ortt]

what Katrina did to Mississippi is what really has me concerned about NYC. I knew it would be bad... but since NYC is more surge prone than MS, the outlook became much grimmer.

Also, the SLOSH predictions are based upon an average sized hurricane in NYC. The hurricane will likely be much larger, possibly throwing off the SLOSH calculations by a category or so

[Jim Cantore]

I'm 15 but I've read/watched worse